makes the name of a consumable unique

makes the column unique and extends the create form to respect the
uniqueness.

app/rollerverbrauch/__init__.py

@@ -9,6 +9,7 @@ from flask.ext.security import Security, SQLAlchemyUserDatastore, \
 from flask.ext.security import user_registered
 from flask_security.core import current_user
 from flask_sqlalchemy import SQLAlchemy
+from sqlalchemy.exc import IntegrityError
 from flask.ext.security.forms import LoginForm
 
 app = Flask(__name__)
@@ -307,11 +308,22 @@ def get_admin_page():
 def create_consumable():
     form = CreateConsumableForm()
 
+    # preinitialize the defaults with potentially existing values from a try before
+    if form.name.data is not None:
+        form.name.default = form.name.data
+    if form.unit.data is not None:
+        form.unit.default = form.unit.data
+
     if form.validate_on_submit():
         new_consumable = Consumable(form.name.data, form.unit.data)
         db.session.add(new_consumable)
+        try:
             db.session.commit()
             tools.db_log_add(new_consumable)
+        except IntegrityError:
+            db.session.rollback()
+            form.name.errors.append('"%s" is not unique.' % (form.name.data))
+            return render_template('createConsumableForm.html', form=form)
         return redirect(url_for('get_admin_page'))
 
     return render_template('createConsumableForm.html', form=form)

app/rollerverbrauch/entities.py

@@ -83,7 +83,7 @@ class Pitstop(db.Model):
 
 class Consumable(db.Model):
     id = db.Column(db.Integer, primary_key=True)
-    name = db.Column(db.String(255))
+    name = db.Column(db.String(255), unique=True)
     unit = db.Column(db.String(255))
 
     def __init__(self, name, unit):